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Reviewer: Frederic Beudot Digital Source: Musical Fidelity A5 CD, Accuphase DP55, Atoll CD200 [in for review] Headphone Amp: Musical Fidelity Xcanv3, Creek OBH11se, Rudistor NX-33 [in for review], HeadRoom Balanced Desktop [in for review] Cables: Zu Gede (RCA and XLR), Consonance Billie interconnects Headphone: Beyerdynamic DT911, AKG K701, Sennheiser HD650 [on loan] Power Cords: Cobalt Ultimate Powerline conditioning: Monster Power HTS5100mkII Sundry accessories: Isolpads under electronics and speakers, Standesign stand Room size: 15' x 30' opening to 3 other rooms. Short wall setup Review component retail: Balanced AKG K701 by HeadRoom ($450 + $300 for mod), Rudistor balanced cable for Sennheiser HD650 ($150)
I owe 6moons readers an upfront clarification. Until recently, I wasn't a headphone enthusiast. Cans are not my main source for musical enjoyment and I used to view them more as a necessity than anything else. Until this assignment that is. I do listen through headphones every week, in the early hours of the day when I am awake and the whole family still sleeps in. Headphones are the only way to enjoy those few quiet hours before the house turns into a beehive; but they've always been a surrogate to a dedicated and insulated listening room as speakers are my preferred listening vessel, primarily because soundstage is so relevant to my appreciation of music and terribly lacking in most headphones. Nevertheless, seeing my listening time through cans increase over the last 12 months, I decided to upgrade my 10-year-old Beyerdynamic DT911 and Creek OBH11-SE amplifier to something more comfortable and refined. That's how an AKG K701 and a Musical Fidelity Xcanv3 made it into my home a few months ago. Seeing this and some available time in my schedule, Srajan suggested a review of Rudistor's NX-33 headphone amplifier, which I gladly accepted to see what an amplifier costing 3 times as much could do against the Musical Fidelity. But the Rudistor is actually a balanced amplifier designed to drive balanced earphones. Testing it single-endedly only would have painted a very partial picture of its abilities. Enter the good folks from HeadRoom who sent me a pair of balanced AKG K701s to compare to my single-ended stock version as well as a pair of Sennheiser HD650s, just because one cannot really judge an amplifier with just one set of cans – and I probably needed another balanced reference amplifier to compare the Rudistor to so I also signed up for a review of the HeadRoom balanced desktop amplifier. I am not quite sure quite how it all happened but within two days after accepting the Rudistor assignment our Editor had solicited from the team, I had 2 amps and 2 sets of cans on my to-do list, in addition to getting accustomed to my personal new gear. And I am not even a headphone geek. But boy am I glad destiny played this little trick on me. I don't know about you but until I looked into the specs of the Rudistor amplifier, I had never heard of balanced headphones and all their supposed benefits. To make things easier and manageable for all of us, I have divided this review into three installments. This first part will look into the headphones, the technology and the differences I heard between single-ended and balanced operation. In a few weeks I'll follow up with
the formal review of the Rudistor NX-33 amplifier and after that, I'll wrap it all up with the review of the fully upgraded HeadRoom Balanced Desktop. Balanced headphones, technology and expected benefits Over 5 years ago HeadRoom was the first company to postulate that driving headphones in balanced mode should yield sonic benefits and they have been working on improving the recipe ever since, now joined by a few other manufacturers like Rudistor bringing their own stone to the edifice. HeadRoom has published a number of very good articles on this technology and I am using their material as a reference in the following introduction. You can also visit the balanced section of their website to find out more about it. The initial assumption was that getting rid of the common ground between left and right channels in a singleended earphone would reduce cross talk and improve sound quality. As it turned out, balanced topology in earphones does that and much more too. A normal headphone cable plug has three connections on it: the tip is left; the ring is right; and the sleeve is ground. The tip connects to a wire that goes to the positive (+) lead of the left headphone driver coil; the ring connects to a wire that goes to the positive lead of the right driver. The sleeve connects to a wire that goes to both negative (-) terminals of the drive coil; this wire usually has a solder joint in the "Y" or in the earpiece where the ground wire from the plug splits into separate wires that are connected to the negative terminals of the driver coils.
Bold lines indicate common return of both left and right channels
The most important thing to note here is that as the left and right channels of the headphone amplifier drive the left and right driver coils, the return current from the drivers gets joined together and travels some distance before returning to the amp's audio ground. This common pathway has some -- possibly significant -- electrical resistance from the wire, solder joints, contact resistance at the plug/jack, and so on, which causes a common signal to appear at the negative terminal of both driver coils. This common signal (a lowlevel summation of the left and right channel) will generate low level cross talk and distortion in the sound heard on headphones.
Balanced headphones are just regular headphones that have been re-cabled in a special way. The normal three-conductor cable with the common ground connection is replaced with a cable that has four conductors: right positive and right negative conductors to the positive and negative connections of the right driver coil; and left positive and left negative conductors to the left driver coil. The cable is terminated in two XLR male connectors, one each for the left and right channel. A special headphone amplifier is used that has "balanced" outputs where each channel has a normal audio drive signal and a mirror image inverted drive signal. The trick here is that there is no "ground" to the headphones anymore, so there is no opportunity for the crosstalk distortion described above. The really interesting thing though is that removing the common ground is only the beginning of the possible improvements from balanced operation. There are different ways to implement a balanced headphone amplifier, the easiest being a single-ended internal design with transformer- coupled outputs. In that case the sonic improvements come from the natural noise rejection of XLR connections (not a major factor in singleended headphones) as well as the common ground removal. But it is possible to go further in the design and operation of balanced headphone amplifiers by using four completely separate amps for all four legs of the signal (right normal, right inverted, left normal, left inverted) as described in the graph below.
The immediate benefit of such a design is that each amplifier only drives half of the coil allowing for a much better control of that coil. It also doubles the effective slew rate (the voltage an amp can swing per second) as both amplifiers are operating in opposite phase to increase the dynamic realism of the music reproduced. Such a design can get fairly difficult to implement with all discrete transistors as they require careful manual matching to ensure that both halves of the signal are amplified identically but integrated chips do remedy this in a fairly elegant and cost effective fashion, allowing entry-level balanced amps to remain quite accessible. If the theory of balanced headphones seems all rosy, there are a few hurdles you need to be aware of. They all relate to the implementation of a balanced headphone system from start to finish.
First, no stock headphone is balanced. Your choices will be reduced to modifying headphones yourself or through a specialized shop. If you are a Sennheiser HD650 or HD600 owner, consider yourself lucky as Sennheiser actually design their cans with miniature terminals on the cord which can be easily replaced, turning one of those to balanced operation into something no more difficult than swapping the stock cord with a balanced one purchased from HeadRoom ($300 for a 10ft balanced Cardas cable), Rudistor (€150 for a 3m cable), Stefan Audio Art ($389 for 10ft) or Moon Audio ($275 for 10ft). Those are the four sources my online searches turned up but I'll reference others if readers are aware of more. If you never fell for Sennheiser's sonic aesthetic or Spartan comfort, your options will be reduced but HeadRoom does offer modified AKG K701s and beyerdynamic DT880s for $300 above their single-ended counterparts and HeadRoom can also modify your own pair of those models for a similar charge. Moon Audio offers a very broad range of balanced modifications for headphones including but not limited to AKG, Sennheiser, Beyerdynamic, Grado, Sony and Audio Technica (they also offer to examine any other cans you would like modified and assess feasibility and cost). I have not heard their modifications so cannot vouch for the quality but they unquestionably offer the broadest range of options. Stefan AudioArt also modifies AKGs and Sennheisers for balanced operation and while I have not heard their mods either, based on Srajan's past experience with his AKG K1000s, I would expect quality to be top notch.
The second obstacle awaiting the upgrading listener is the choice of amplifier to drive his or her now balanced headphone. Rudistor and HeadRoom both offer complete lines of balanced headphone amplifiers and Ray Samuels very recently announced its new flagship Emmeline II B52. Rudistor's line ranges from €950 ($1200) for the NX-33 to €3500 ($4400) for the fully-discrete, quad-mono RP010-B MkII. HeadRoom offers balanced headphone amplifiers in 3 of its 5 lines (Desktop, Home and Max), ranging from $899 for the basic balanced Desktop to $5597 for a fully upgraded Max balanced amp with DAC. Ray Samuels' $5350 B52 is a combined pre-amplifier and balanced headphone amplifier with separate power supply but might suffer one handicap versus Rudistor's and HeadRoom's top offerings. The B52 does not have a phase splitter on its single-ended inputs, meaning that despite its balanced topology and connections, it will operate in single-ended mode and shorts pin 3 to ground unless fed a balanced input signal, therefore losing most of the benefits of a truly balanced design. It's not an issue i if you have access to a balanced source but a lot more problematic if like me you enjoy one of Musical Fidelity's CD players devoid of balanced outputs. Maybe the improved sound quality of the B52 is worth this small sacrifice, I don't know. I have not found any other manufacturer of balanced headphone amplifiers but if readers know of others, I'll be happy to add them in future installments to highlight as many choices as available.
The final challenge for the candidate to balanced bliss is to pick one or more sources to listen to. As indicated already, Rudistor and HeadRoom make it easy for you by incorporating a phase splitter after the unbalanced inputs of the amplifier, allowing fully balanced operation of the amp and fully balanced drive of the headphones regardless of the source used. My Accuphase has both balanced and unbalanced outputs which I ran separately into the Rudistor NX-33 with balanced and single-ended lengths of Zu Gede interconnects. I could detect some very faint differences between both types of connections, mainly a more relaxed top end and a slightly lower noise floor in favor of the balanced connection - but I sincerely doubt I would notice it in normal operation outside of critical listening. A significant fraction of modern CD players have balanced outputs, some sounding much better than their single-ended outputs (think Esoteric and their fully balanced players), most sounding from just different to absolutely identical in both modes. One I heard a few years ago actually sounded worse in balanced mode (I'll keep the name of this now defunct brand unmentioned as you have little risk of running into it even on the used market). Phono cartridges are a naturally balanced source but unless you have the arm rewired, most today come with RCA outputs. Balanced phono preamps are about as rare as balanced headphone amps and cover an even wider price range. With PS Audio, AQVOX and Moon offering balanced phono preamps for less than $1500 and BAT's $8,500 VK-10SE and FM Accoustics' €19000 FM222 MkII, I have pretty much exhausted my knowledge of balanced phono preamps.
One of the most elegant ways to provide headphone listeners with a balanced source may actually have been implemented by HeadRoom who offer a fully balanced DAC upgrade for their three lines of balanced amplifiers. By feeding the digital signal to a separate DAC on each side and allowing them to generate both the normal analog output and its anti-phase equivalent, they generate a perfectly matching balanced signal for the twin amplifiers in each channel. As the
Desktop amplifier sent to me for review is equipped with this option, I'll be able to report on how efficient this solution is. And I left the best part for last since this DAC also has a USB input which will allow me to feed it directly from my laptop, jitter free. All this is to say that going balanced will cost you at the very least $1200 (amplifier plus balanced cable for a Sennheiser), and another $200 if you want to add a balanced DAC (still the cheapest option to go balanced from source to headphones, excluding a computer which I assume you own since you are reading this review). A more advanced system will set you up north of $2000 to $2500 and a top-of-the-line system close to $6000 excluding a source which can cost as much as your pockets are deep. Yes, it is possible to spend even more on a single-ended system but it is also possible to set up a satisfying single-ended amp and headphone combination for less than $1000 with greater choices. So are balanced headphones really worth it?
Balanced headphones - how they sound. As you all know, a key to reviewing is to only change one element at a time to assess its sonic impact. In this particular case, it was not possible as both the topology and the headphone cables were different between balanced and single-ended versions of the headphones I had. To keep it simple, I'll talk about the sonic characteristics of the balanced or single-ended version but keep in mind that it entails the sonic signature of the associated cables as well.
To assess the differences between SE and balanced operation I listened to both the AKG K701 (two sets of cans, one stock, one with Cardas balanced cable) and Sennheiser HD650 (only one set of cans, swapping
between the stock and Rudistor's balanced cable) through both the Rudistor NX-33 and Desktop balanced (as both amps can drive both types of cans but obviously only using one internal amp per side in SE mode versus two in balanced operation). I took notes of the differences I heard between both modes with both amps – the differences that were common regardless of the amplifier I attributed to SE vs. balanced operation, the differences I heard only with one amp I considered to be amp specific and not a result of the operation mode (and I'll highlight those in my reviews of the amplifiers). All listening was done using the Atoll CD200 in for review as a single-ended source.
The first thing to highlight is that the nature of the changes was mostly identical between the Sennheisers and AKGs but the relative intensity of the changes varied between both headphone brands. The stock AKG K701 has been reviewed by multiple publications so I am not going to describe its sound and performance in many details except for a few elements that are relevant to this evaluation. The first one and most often voiced criticism of the AKG is its relative lack of bass (or its extremely tight bass depending on your optics and preferences). Balanced operation was able to extract much deeper bass from the K701 without losing grip or control over it. There was simply a far more physical feeling to the lower registers, probably still insufficient to satisfy a bass hound but certainly enough to satisfy anybody feeling the AKGs to be just a little lean and dry in the lower octaves, without going overboard and becoming loose or wobbly. The Rudistor actually went a little further than the Desktop balanced in its ability to pull bass out of the AKGs but both amps made a very substantial improvement). It was very obvious on all recordings with any sort of bass extension but it hit me particularly when listening to Saint-Saens' Carnaval des Animaux [EMI CDM 7691122]. Its double basses represent an elephant and for the first time I actually felt the pachyderm's heavy footsteps shake the bones of my head.
A second trait of the AKG is its musical transparency and again I found the balanced cans much superior in their ability to retrieve musically relevant details (as opposed to brightly enhancing all details) and position them properly in the musical flow. I have been wondering if this was a result of the increased control over the voice coils or just the naturally lower noise floor provided by balanced operation. The last element I noticed is that the stock AKG is the headphone with the widest headstage I have heard so far but the balanced version goes much further on that aspect, with a very wide stage but still very little sense of depth. Whether this is due to the lack of cross talk or the deeper bass better rendering ambient cues or the increased level of
details (or all of the above) I can't say but the improvement was significant and returning to SE operation felt as though walls were closing in around my head.
Another critic often leveled against the AKG K701s is their somewhat recessed midrange. I could not agree more. The Rudistor NX-33 in balanced mode did a fantastic job giving flesh and life to their otherwise timid midrange but I did not detect quite the same level of improvement with the HeadRoom amp although there was some improvement too. One thing that balanced operation did not affect is the incredible elegance of the AKGs, their refined treble, their talent with tones and their uncanny ability to reveal music hidden deep in any recording, all which makes them such unique earphones in my mind. Sennheiser owners are in for a treat too with balanced operation. Swapping cords is a 30- second deal and not permanent. Your headphones will still work on other single-ended amps you may own, not the case for the AKGs or Beyerdynamics which get permanently rewired. The flip side (there has to be one) is that the Sennheiser contacts between cable and phones aren't soldered and I heard static in one ear on a few occasions as I was moving about (it was a rare occurrence in normal use but fairly easy to reproduce by wiggling the cable at the contact point, raising the question of durability). Besides that, the major impact was better control of bass notes. The balanced HD650 went deeper than its SE version and bass got tighter, a little faster and quite more detailed even though not quite of the AKG caliber in that last department. Overall it lost most of the excessively laid-back (some might say boring) character which the HD650 exhibits in SE mode. If you think the HD650 a little ripe at the bottom or lacking dynamic and leading edge emphasis, balanced operation may just be what your doctor ordered. All in all the Sennheiser gained speed and dynamic contrast as well as detail in balanced mode but not to the point of changing overall character. It was more a tightening of bolts here and there and injecting a serious and welcome shot of adrenaline (the HeadRoom Desktop balanced pulled that act in a far more convincing fashion than the Rudistor). Shostakovich's 11th Symphony's final movement will tax any speaker or earphone-based system with its gigantic orchestral masses roaring forward while a bell strives to be heard above the mayhem. To add to the challenge, Inbal's version with the Wiener Symphoniker [Denon CO-78920] is somewhat congested but the HeadRoom and balanced HD650 did reproduce the full weight of the orchestra without flinching while allowing the bell to resonate in the distance with a clarity I had never heard before. Finally, balanced mode allowed the HD650 to broaden its soundstage quite significantly, nothing as spectacular or wide as the AKGs but clearly less localized between the ears as the stock phones do.
Unfortunately from my perspective, balanced operation did not solve all the quibbles I have with the HD650, namely a nasal midrange and a top end devoid of elegance. Even the Rudistor that worked wonders with the AKG's midrange was not able to bring life and credibility to this part of the HD650's musical reproduction, squeezed as it is between a deep and slightly booming bass at one end and a somewhat bright and stiff treble. Neither did balanced operation change the fact that those cans are plain uncomfortable after a couple hours, mostly because the pressure they exert on one's temples is far too great. The AKG by comparison is almost non-existent.
The bottom line of these few weeks spent with various pieces of balanced headphone equipment was that the improvements brought about by balanced operation were real and very significant. If you own a Sennheiser HD600 or 650, a beyerdynamic DT880 or an AKG K701 and are considering spending money on upgrades (of cans or amp or both), I strongly encourage you to look into balanced operation. The reason is fairly simple. You will never enjoy this kind of improvement by working your way up the curve of diminishing returns unless you spend considerably more than it will take to jump to the beginning of another curve, this one with the tremendous potential of balanced operation. If you are a Grado, Audio Technica or Sony lover, your options are more limited but I would predict you would have a lot to gain by going balanced as well.
All in all, balanced operation sounds so much more real and present, more dynamic and detailed. If you are looking for a dramatic improvement to your headphone, I can't see a more cost-efficient way to do so. In the
next two installments, I'll tell you a little more about the balanced amplifiers - two very different sounding animals, two contestants worthy of your attention.
Reviewer: Frederic Beudot Digital Source: Musical Fidelity A5 CD, Accuphase DP55, Atoll CD200 [in for review] Headphone Amp: Musical Fidelity Xcanv3, Creek OBH11se, Rudistor NX-33 [in for review], HeadRoom Balanced Desktop [in for review] Cables: Zu Gede (RCA and XLR), Consonance Billie interconnects Headphone: Beyerdynamic DT911, AKG K701, Sennheiser HD650 [on loan] Power Cords: Cobalt Ultimate Powerline conditioning: Monster Power HTS5100mkII Sundry accessories: Isolpads under electronics and speakers, Standesign stand Room size: 15' x 30' opening to 3 other rooms. Short wall setup Review component retail: Rudistor NX-33 €950; balanced AKG K701 by HeadRoom ($450 + $300 for mod), Rudistor balanced cable for Sennheiser HD650 ($150)
In the first installment of this series on balanced headphone operation, I looked into the technology and its benefits and concluded that it was a very credible and cost efficient way to improve headphone enjoyment by a significant margin. Here comes the report on the headphone amplifier that started my journey into balanced headphone country - the Rudistor NX-33. Rudistor is a fairly recent company founded by Dr. Rudi Stor in Italy in 2003. The firm has come a long way in its four years of activity. Even if its main line of business is headphone amplifiers, Rudistor also offers two power amplifiers of somewhat unconventional design. The first one is a single-ended solid state power amplifier with zero negative feedback delivering 2 x 10 watts in pure class A (the RR20 at €1500). The second is a single-ended all tube amplifier using KT88s in triode mode to deliver a full 5wpc also in pure class A (the RR88 at €1900). Rudistor's catalog further includes balanced headphone cables for the Sennheiser HD650s and HD600s as well as two RCA interconnects. Rudistor's headphone amplifier line is extremely complete and almost everybody will find a component suitable to their budget and desires. The line consists of three single-ended solid state amplifiers, the NX-01 SE (€475), NKK.01se (€990 including an internal USB DAC) and RPX33 Dualmono (€1300); three hybrid amplifier adding dual triodes in the input stage while keeping class A bipolar power transistors for the current stage and ranging from €700 (RP 5.1) to €2100 (RP7B); and two tube amplifiers for electrostatic earphones named Egmont and Egmont Signature (€1300 and €2900 respectively, the signature beingavailable also in balanced guise for €3500). In the center of the line are Rudistor's balanced amplifiers, starting with the NX-33 and moving up to the two Quad Mono designs (the RPX100, which doubles as a preamp for €2250; and the no-compromise RP010-B MkII for €3500). Then there is the conceptual RP1000 into which Rudi as he is now known on all dedicated headphone forums has packed all his knowledge of amplifier design coupled with the best parts money can buy. The RP1000 is a concept amplifier not designed for commercial production even though three of the
four built to date have found an owner. At €10,000 per unit and 3 months of lead time to manufacture, they are definitely not mass-market but Rudi has parts to produce another three or four and then the RP1000 will probably go the way of the dodo. If you have deep pockets and are interested in owning an amplifier representing the ultimate a talented designer can create, act soon. If you have read the previous paragraph attentively, a few things should be obvious by now. The first one is that all prices are listed in Euros and your credit card will be billed in Euros if you purchase through Rudistor's website (a virtual shop through Amazon.com is also in the works but not active as I write this review). The final price in your local currency will depend on the exchange rate of the moment as well as the fees charged by your credit card company. The good news is that all prices include international shipment through FedEx.
The second thing that should be clear by now is that Rudi's naming convention owes more to the Da Vinci Code than any other brand I have encountered. I am still working on the secret cipher I know must reside within. Before I move on to the NX-33 specifically, I believe it important to highlight a few elements of Dr. Rudi Stor's philosophy that are relevant to all his products and will complement my listening impressions to help understand how intentions actually translate into sonic characteristics. I have reproduced below two extracts from Rudistors' company profile that to me exemplify all I enjoyed during this review of the NX-33: "Our mission and philosophy is to design and produce the highest quality audio electronics with the least compromise possible and with no prejudgments on components and circuitry topology, in order to reach the highest real-sound feeling." "We always compare our sound with real life sound. All our team members have direct experience with music, playing instruments, being part of a group or working in recordings, and as 'Company Policy' at least one live concert a week must be on our agenda.[...] Music is our passion." I don't know if Rudistor's design team really does attend a concert every week but the NX-33 surely comes
close to their ultimate goal of sounding real. The first extract though is also meaningful because Rudi's designs have often been called old-fashioned on headphone forums. Obviously, Rudi cares more about results and quality of implementation than design originality for the sake of originality. That's very obvious in how production is set up between two labs controlled by Rudistor, one in Italy, the other in Austria. Both are using high-quality parts purchased through German and Swiss vendors to ensure that only highest-grade components make it into your amplifier. As importantly, all amplifiers find their way back to Trieste's R&D lab for thorough testing before they get shipped to their final destination - not the most cost-efficient supply chain but one that ensures the level of quality and service Rudistor wants to offer their customers. Nonetheless, work is in progress to implement a production lab in the US for the models using integrated chips which require a slightly less demanding level of quality control. The all-discrete amplifiers like the balanced Quad-Mono designs will continue to be manufactured and controlled in Europe since they require careful parts matching in each channel and Rudi only entrusts this task to a very few and qualified hands.
By now you probably think that I have spent too much time telling you about the company and not enough about the product. Still, I always find it interesting to learn about a designer' philosophy when it so clearly shapes the company he or she created and how it operates - when the company becomes the vessel to achieve a goal, not an end in itself. For those of you whose patience I have exhausted and who are more focused on the destination than the journey, the Rudistor NX-33 is the dream of a music lover come true and should rightly belong in Jeff Day's Music Lovers series. If you are into record monitoring, ultra-detailed reproduction and use headphones as magnifying glasses to hear a second violinist fart in the middle of Beethoven's Fifth, then the NX-33 is not for you. If you enjoy listening to music (any music, really) late into the night while savoring a glass or two of Valpolicella (a single malt will do too but I would suggest smaller quantities); and if you care more about the forest than the ant on the bark of the fifth tree starting from the back, then come along. The Rudistor will enchant you.
The NX-33, like all Rudistor amplifiers, is strongly built and at 4.5kg (9.9lb) with a fairly low profile (7cm high or 2.8") a fairly dense little box. At 30cm (11.8 inches), it is 1cm deeper than the Atoll CD200 CD player currently in for review but only half as wide (24cm or 9.4 inches). I particularly enjoyed the thick brushed aluminum front plate which perfectly matched the style of the Atoll and Musical Fidelity CD players in my living room. As all married audiophiles, I am very quickly learning how to become style-conscious. It's a necessary survival skill.
The NX-33 has clearly been designed with high-end sensibilities. It offers a detachable power cord allowing you to swap the stock one for any aftermarket cord you fancy. The best part about it is how very well it responded to my fairly basic Cobalt Ultimate power. You might be rewarded even further should you decide to feed it through a cord costing more than the amplifier itself. If that sounds a bit sarcastic, you've got a point but the NX-33 truly responded to a better cord by displaying greater bass control. Secondly, the gold-plated RCA and XLR connectors are bolted to the chassis for a very sturdy feel and just as importantly, are placed far enough apart to allow the use of whatever locking RCA plug you want. I have to admit to getting tired of components which place the left and right RCA connectors so close together that it's almost impossible to lock the connectors without rubbing them against each other or pulling them sideways. Kudos to Rudistor for smartly using the extra room their enclosure provides. There is only one thing in the NX-33 design that was a mild annoyance - the absence of a tape loop or bypass. It is not a problem when using a preamp or integrated amp with a line-level output but my Onix SP3 integrated in the office system does not have such a provision and I could not insert the NX-33 into the system without disconnecting the SP3 from the CD player first. That's not a big deal really but seeing how much space remains on the NX-33's back, perhaps a thru-put could be added to the next generation of this amplifier? I know that true headphiles have dedicated systems but I can't be the only one left to use the same source for both headphones and speakers. Or can I?
A few more design details are worth mentioning before we move to the listening section of this review. The NX-33 does not have a gain switch but I did not encounter any problems driving the headphones on hand to satisfactory levels by setting the continuous pot somewhere between 9 and 11 o'clock. In single-ended operation, I of course needed to set the dial higher to reach the same sound pressure (for both the AKG K701 and Sennheiser HD650) but I never exceeded 11 o'clock. Even though I do not listen at ear-splitting levels, I doubt anybody would have an issue driving most commercial earphones to ear-bleeding agony. It would be a terrible waste but I don't think there are laws prohibiting it - yet. As I mentioned in the introduction to balanced headphones, the NX-33 is equipped with a phase splitter after the RCA input, meaning that whatever signal you feed it (balanced or single-ended), it will operate in fully balanced mode thereafter. I was very appreciative of this solution as my reference CD player does not have balanced outputs. Nonetheless, I was able to enjoy almost all the benefits balanced operation has to offer. Do not listen to the sirens insisting that you absolutely need a balanced source to fully enjoy balanced headphones. From the introduction, you will also recall that the benefits of balanced mode really fall into two categories, those coming from the common ground removal accessible to all balanced amplifiers; and those only accessible by a fully balanced designs. The NX-33 is of this latter category, meaning that it uses four separate amplifiers, one for each of the normal and inverted legs of the signal on each channel. To keep costs under control, the NX-33 was designed around four single-ended ICs with tight specifications operating in pure class A (the amp does get warm but not too hot to touch by any means). Its mightier and costlier brethren, the RPX-100 and RP010B MkII, replace those integrated chips with discrete components. The NX33 is also equipped with a single-ended headphone output which is active at all times in parallel to the balanced outputs. Alberto Gomez, Rudistor's representative for the US and Canada, indicated that there was no issue with running two headphones simultaneously from each output but I did not tried it myself.
It was through this ¼" plug that I first sampled the NX-33 as the balanced headphones had not arrived yet. To tell the truth, it was not love at first listen. Even though it was already broken in, compared to the Musical Fidelity Xcan, the NX-33 had less dynamic contrast, was less detailed and had a hard time extracting bass notes from the single-ended AKG K701. It sounded flat and dull overall. I have since learned to appreciate the subtle nuances the NX-33 is capable of and which the X-can has no idea even exist. Overall however, I stand by my first impression. Using the NX-33 single-endedly is just wasting $1200. Half that amount can bring as much if not more to the table (and I am sure that Rudi's SE amps would do that just fine as well). Until you have tried the NX-33 balanced, you won't have any idea of what it is really capable.
When I finally plugged in the balanced AKGs, it did not take very long before I realized I was dealing with a different amplifier of the same smooth signature sound but now energized and dynamic. The first thing I noticed was its silence. Blacks were darker than the night. This amplifier has no hum, hiss, noise, static, nothing at all. I thought the Xcan was fairly silent but in operation, the Rudistor proved to be simply free of any noise, the direct benefit of which was that details rose effortlessly over this dark background.
The NX-33 is reasonably detailed but it does not go at it by adding a silver lining to the music. It simply lets the details float naturally to the surface as the music dictates, not forcing any forward if that's not where it belongs. From that perspective it reminded me of my dear FJ OM speakers that deliver details in the same fashion, with nothing forced or artificial - no magnifying effect.
The second trait the NX-33 shares with the FJ speakers was tonal density and richness. I have recently rediscovered an Erato recording of Vivaldi's Concerto for two mandolins by Claudio Scimone and I Solisti Veneti [Erato 2292-45203-2]. Through the Rudistor NX-33 and AKG K701s, I could clearly differentiate both mandolins, not just their mere locations but tone colors. The nuances of sonority that my Mc2275 and FJ OMs only hinted at where rendered very clearly through the headphones. The
second movement of this concerto is a very touching duo for mandolin and through the NX-33 I could hear both the metallic voice of the instruments and the more woody timbres of their bodies in all their hues - fully captivating and enthralling.
I had to force myself to listen with this level of analytical attention. The main strength of the NX-33 was to draw me deeply into the music. More than once did I settle with my note book only to re-emerge over an hour later without a single word written down. This was the hardest part of this assignment, coming back from a deeply emotional involvement into the music to find words that would describe accurately what the NX-33 sounded like. I spent a lot of time going through my records of the 1960s to enjoy them through the Rudistor. There were multiple reasons for that. For one, the NX-33 lets tape hiss sound natural, not bright, aggressive or disturbing, just a gentle reminder of the age of the record lingering in the background but easy to forget to focus on the music. The second reason is related to the richness of tones already mentioned which those old master tapes have in spades. The NX-33 does full justice to the tonal richness of those records. Finally, whenever remastering was done properly, those recordings have tremendous micro and macro dynamic life and the NX-33 served both faithfully. It was capable of great swings while preserving all the small ripples of sound the microphones captured.
Sviatoslav Richter's recording of Beethoven's Piano Concerto No.1 with Munch and the Boston Symphony, recently reissued by RCA [BMG 82876-59421-2 classic library] is one such recording with Richter's typical gigantic sound and physical domination of the instrument. His use and abuse of dynamic contrasts while loading each note with multiple layers of tonal subtleties has never come across as it did through the Rudistor and AKG. If you have never heard Richter's very physical rendition of the Appassionata recorded on the same disc, be prepared to be overwhelmed. The NX-33 reproduces a piano with its full scale and harmonics unrestrained, a treat that my speaker system is not fully capable of. As Richter uses the full extremes of the piano's dynamic capabilities, the effect is impressive to say the least. If the NX-33 in single-
ended mode struggled to deliver the bass notes, there was no worry about it in balanced mode. The bass was deep, tight, rich and detailed, as if it were really about two different amps. In a way it is, with four versus two ICs driving the voice coils of the earphones.
Another set of discs that have spent a lot of time in my CD player of late is Callirhoé by Andre Cardinal Destouches. This recreation by Herve Niquet and Le Concert Spirituel is probably the very best interpretation of music from the mid 1700s I have ever heard [Glossa GES 921612-F]. This period lost between Lully and Rameau and politically characterized by decadent regencies is mostly forgotten today and so are most of the composers who illuminated those days. Who remembers Mouret, Collasse or Destouches? Only Campra's Requiem saved him from absolute anonymity.
Destouches' work of all the masters of this time is probably the most worthy of resurrection and Callirhoé is a perfect example. As with all of Glossa's editions, the recording quality is exceptional, balancing intimate portrayls of the musicians with a perfect rendition of the concert hall acoustics. The orchestra on period
instruments has all the required acidic and metallic tones characteristic of the era but the NX-33 manages to keep them from being aggressive as is so often the case with lesser electronics. I have kept the most impressive part for the end though. The NX-33 is a giant when it comes to vocal reproduction. As I have pointed out a few times already, no component will get my attention if it can't reproduce the life of the human voice accurately (that's a minimum) and with all its emotional content intact (that's the Graal). On both accounts, the NX-33 scores an A. Paired with headphones as transparent as the AKGs, you can hear into the midrange as deep as the recording and source allow yet nothing sounds forced, contrived or out of place because voices come
through rich and smooth, detailed and clear, so near, present and real yet supple and sweet. When it comes to midrange reproduction, the NX-33 and AKG are kings of paradoxes, perhaps what sounding real is all about.
Going back to Callirhoé, a young counter tenor I had never heard before, Cyril Auvity, inhabits the part of Agenor. He is one of the most expressive Haute-Contres I have heard in recent years. The increased interest in baroque music over the past 20 years has seen quite a number of new counter-tenors appear on international scenes and that's fantastic as that tessitura had almost disappeared. Unfortunately, many confuse mannerism with authenticity and technique with emotion. Cyril Auvity's refreshing interpretation is a good reminder of what the differences should be. Served by the NX-33 and AKG, I could feel I was there in Metz a year ago when he was putting all his sensitivity into his singing. Awesome.
At this point in the review, it is time for me to tell you that the NX-33 is not perfect though if it were otherwise, there'd be no need for Rudistor's more ambitious designs. A few things come to mind after hours of careful listening. The NX-33 achieves its non-fatiguing, non-aggressive and rich sound by making a few concessions. First off, the leading edge of notes is clearly rounded and smoothed which contributes greatly to the feeling that one can listen forever without suffering fatigue. Simultanteously, it gives the NX-33 a somewhat more relaxed and slower presentation than the Headroom Desktop that I'll review in the coming weeks. If you pair the NX-33 with laid-back cans like the Sennheiser HD650s, it will clearly go too far into the peace and love side of things and veer directly into boredom. The same thing will happen if you pair the NX-33 with a laid-back source. What you need is detailed neutrality for both source and cable and then let the NX-33 do the seasoning. Let it add texture, richness and smooth sweetness where it excels. This brings me to the second area where Rudistor hopefully goes further with the discrete designs - low-level detail retrieval. I know I started by saying that the NX-33 does details well and allows them to surge over dark backgrounds. That is true yet the Headroom Desktop goes even further in its ability to retrieve ultimate minutiae (though sometimes it goes too far as we will see). The NX-33 errs on the side of ignoring the finest of details in order to avoid sounding clinical. I can only applaud that choice but the very best tube amps I know do both, musicality and detail. To be fair, none of those cost $1250 and I would bet that Rudistor's Quad Mono designs make significant improvements in that area. Finally, the NX-33 falls a little short in sheer drive power and depth of bass (as well as control) vs. the Headroom Desktop. That's another reason why I did not find the match with the HD650 as synergistic as that
with the AKG which naturally has very tight bass and welcomes the slight mid-bass bloom the NX-33 contributes. Again I feel the discrete designs should be able to go further in bass drive and control without sacrificing any of the fantastic musicality the NX-33 offers. Bass in Peter Gabriel's So is of the highest quality -- deep, solid and detailed -- but the NX-33 could not recreate it with the full size, control and impact the Headroom Desktop is capable of. The NX-33 does not do excess. It does refinement and elegance but in this particular instance, excess may actually be closer to the truth.
I have kept my biggest beef with the NX-33 for last. It is an addictive drug! Yet it will have to return to Rudistor. Thousands of dollars in house repairs are awaiting me this spring so the NX-33 must leave though I don't look forward to saying goodbye. When paired with the balanced AKG K701 (and I would bet that all transparent and clear-sounding earphones would fair very well), it has deeply and permanently changed my perception of what a great earphone amp can do - and it's not just more details. Over the more than two months that I have been listening to the NX-33, it has grown as a more important part of my musical enjoyment from day to day. It is not a monitoring tool nor even a reviewer's tool since it has too much of a personality to allow proper evaluation of other gear. It is a musical instrument designed to provide as much enjoyment of music as possible, focusing on the musical flow, not just the notes. As I was wrapping up, I wanted to leave you with a few words that would best describe the signature sound of the NX-33. Organic was the first one that came to my mind, involving the second and elegant the last. Maybe that's all I should have written but you may not have believed me had I not gone through all the audiophile attributes first before finally concluding that they don't really matter when it comes to the NX-33
Reviewer: Frederic Beudot Digital Source: Musical Fidelity A5 CD, Accuphase DP55, Atoll CD200 [in for review] Headphone Amp: Musical Fidelity Xcanv3, Creek OBH11se, Rudistor NX-33 [in for review], HeadRoom Balanced Desktop [in for review] Cables: Zu Gede (RCA and XLR), Consonance Billie interconnects Headphone: Beyerdynamic DT911, AKG K701, Sennheiser HD650 [on loan] Power Cords: Cobalt Ultimate Powerline conditioning: Monster Power HTS5100mkII Sundry accessories: Isolpads under electronics and speakers, Standesign stand
Room size: 15' x 30' opening to 3 other rooms. Short wall setup Review component retail: Headroom Balanced Desktop ($1696 as reviewed)
Headroom's Balanced Desktop is the third (and, at least for now last) installment in my exploration of balanced earphone operation; Part I looked at the technology and Part II reviewed the musically highly involving and organic Rudistor NX-33. Let me clarify one thing upfront. This review will not be a shoot-out between these two amps. They both have strengths and weaknesses. They have to at this price point. Plus, they don't even target the same audiophiles so a head-to-head comparison of all sonic attributes would be of little value though when there are fundamental differences, I'll point them out to support a more informed choice. If I have a favorite at the end, it does not mean it should be yours. That's what the thousands of words after this introduction are all on about. HeadRoom has been at the forefront of headphone amplification for years, first initiating the world to the idea that there is a lot more to headphone listening than the anorexic output of integrated amplifiers or receivers would suggest by introducing the audiophile community to dedicated earphone amplifiers, a category of gear whose utility none of us would question today but which was far from a home run when Tyll Hertsens first started on his quest.
Once this battle had been won (something the number of dedicated amplifiers on the market and the range of technologies employed would attest to), Tyll did not stand still. He pioneered another revolutionary concept, balanced amplifiers and headphones, taking musical reproduction another giant step forward in cost-conscious fashion. For the past five years, Headroom's lineup of balanced amplifiers and modified cans has been progressing and growing. At the very top sits the Max Balanced ($3999 to $5597 depending on options), which is capable of driving 2 pairs of balanced headphones in pure class A balanced operation without a sweat. Second from the top is the Home Balanced ($2296 to $3596) which allows access to most of the Max's modules and qualities in a more affordable package. Finally there is the object of today's review, the brand-new Desktop Balanced ($899 to $1696 depending on options), an exercise in miniaturization and cost containment aimed at offering most of the benefits of balanced operation in a more manageable fashion. Headroom also offers three earphones converted for balanced operation (beyerdynamic DT880, AKG K701, Sennheiser HD650) for a surcharge of $300 over their single-ended counterparts and will modify any of these models for you should you already own them. At the time of this review, Headroom offers this headphone modification free to any customer purchasing a balanced amplifier and a pair of headphones from them. That's a $300 discount for a package acquisition. The single-ended Desktop amplifier has been thoroughly reviewed in many publications, including by Ryan Clarin in these pages. Hence I won't spend much time going over all its features and basic sonic characteristics. Instead, I will focus mainly on the key differences between single-ended and balanced operation. Neither will I spend a lot of time on the benefits of and technology behind balanced drive. Those were covered in detail in Part I and II of this triptych.
The first balanced difference you will see versus a single-ended Desktop is obviously on the front face. The customary ¼" and mini outputs have been replaced by two balanced female connectors (one left, one right), but those clever connectors also host a ¼" plug in their centers, allowing the Balanced amp to drive either one pair of balanced phones or two pairs of conventionally single-ended ones. Since I will not return to single-ended operation, let me just say here that it was surprisingly powerful and dynamic. While there was no mistaking the differences with balanced operation, the performance gap did not seem as large as with the Rudistor, a nice benefit for those planning to stay with both technologies. Also gone from the face is the brightness switch which allowed listeners to dial in an HF boost to offset the impact of the cross-feed circuit. It seems lack of internal space was the cause for this feature's elimination but in all fairness, not once did I miss top-end sparkle. The cross-feed circuit remains and I'll refer you to Ryan's review for the specifics. Besides adding a little weight in the bass, I really did not detect any major changes in soundstaging when engaged. That should not come as a surprise. The AKG K701 is a soundstaging champion by headphone standards and balanced operation all by itself improves this attribute significantly. The contribution from the cross-feed circuit under those conditions was very minimal. When used single-endedly with the HD650 (the other end of the headphone spectrum with a fairly narrow and centered presentation), the cross-feed benefits were more obvious but again not radical though pleasant. After playing with the switch a few times over the first few days, I left it on for the rest of the reviewing period and completely forgot it was even there. The second switch on the front face sets gain between low, medium and high to adapt to specific earphones. The Desktop I reviewed was equipped with the $199 stepped attenuator upgrade which made use of the gain switch even more critical than it would have been with the standard Alps Pot. With the switch on high, I could barely move past 8 o'clock on the volume control and the steps where just too coarse to find a comfortable level. On medium gain however, I had to turn the volume control all the way to 1:00 or 2:00PM to get the dynamic contrast I knew the amplifier to be capable of. After a bit of tinkering and experimentation, I found settings that suited me. Eventually I found another solution by using high gain, attenuator set to around 10 o'clock, signal routed through the internal DAC and Foobar2000 set to digitally adjust volume levels, actually restoring a continuous if virtual volume control (Foobar's volume adjustments are made in 0.15dB increments).
On the back of the amplifier things have changed as well for the balanced model. It is now equipped with a
set of balanced inputs added to the RCAs. The choice between either is made by switch. It allows connection of two separate analog sources and toggles between them although it would have made my life much easier had the source selection switch been located on the amplifier's front (the fully upgraded Desktop sports three such switches in the back, a two-way to toggle between digital and analog input, another to choose between balanced and single-ended analog and a three-pole switch to select from between USB, coaxial and optical digital inputs). Overall construction and feel are very sturdy, with inputs bolted to the chassis and spaced far enough apart to allow for even oversized connectors, a great achievement considering the crowded real estate and something competitors should emulate. The only thing missing on this back panel is a tape loop but honestly, I don't know where Headroom would have fit it. There just is no available space.
Another visible change is the introduction of the new Astrodyne power supply that offers more current on demand for the Balanced Desktop Amp without having to shell out for the $399 HeadRoom Desktop Power Supply. The Astrodyne is also available separately for $99 to supply the rest of the HeadRoom Desktop and Micro amps, purportedly offering performance gains over the previous linear AC wall-wart included with HeadRoom Micro and Desktop models. The most important changes between single-ended and balanced Desktop amplifiers took place inside of course to accommodate fully balanced operation. The first and most welcome of those is the phase splitter inserted past the single-ended inputs to convert to fully balanced operation regardless of signal. The second change was obviously to adapt the amplification stages to fully balanced mode. The Balanced Desktop can also be upgraded to balanced Home power module, adding the benefit of pure class A operation to the 4 discrete amplification modules necessary for balanced stereo operation.
If you add it all up, the $1,297 review unit had all the possible musical upgrades (Home module and stepped attenuator) plus the $399 optional Home DAC to come in at $1,696. I can't say how any of those upgrades compare to the stock options and whether they constitute a worthy investment but I can clearly say that the
qualities and weaknesses found in the upgraded Balanced Desktop did not seem out of line with the asking price. The amplifier clearly outclasses cheaper amplifiers in my house while not exhibiting all of the qualities one would expect from some of the more ambitious designs available, albeit at a much dearer price as well. The most obvious characteristic of the Balanced Desktop is its ability to drive earphones in fast-and-furious style. Even though made and designed in the US, it clearly belongs in the PRaT family our British friends so clearly favor. The Desktop's emphasis is on the leading edge of notes, on timing and details small and large, not so much on note decays and all the subtle variations of tone that can inhabit a note. The Desktop does not take much time to linger on, it is always already moving on. Another of its strengths is bass reproduction deep and tight, lean without being dry, alive with low level details.
These sonic strengths were absolutely fantastic on Renaud Garcia Fons' Arcoluz [Enja, ENJ-9478-2], a firework of complex rhythms with upright 5-string bass, guitar and percussion intertwined. The Desktop reproduced the deepest bass notes and all the low level detail coming from the archer stroking the strings, the metallic and diabolically tricky rhythms of the gypsy guitar and the tight and purposely dry impact of the percussion. Playback of this disk through the Desktop and AKG K701 had me on the edge of my seat from start to finish. Even the Rudistor NX-33 could not quite keep up with the frenzied speed and deepest bass of the Desktop.
The Desktop Balanced really shone on all recordings thriving on speed and bass muscle. All of my U2 disks got a lot of play through the Desktop. So did REM's Best of. All of these discs took on a new life mainly down below that I did not know they were hiding. Even my wife borrowed the amp a few times to listen to the Gorillaz' G Side (but she did like the HD650 better than the AKG since you can't have enough bass for the Gorillaz, can you now). The flip side of this was that the HeadRoom could sound somewhat hurried with discs requiring more finesse and subtlety. If you have read Part I and II, you already know that classical vocal music is one of the yard sticks by which I measure any gear. Here the Desktop had a few shortcomings. Before I became fully aware of and understood its somewhat brighter nature and emphasized upper midrange, I paired the HeadRoom with Atoll's CD200 and Zu Gede interconnects. The Atoll is not bright or dry by any means but has a more open and airy midrange than my Musical Fidelity A5 or Accuphase DP55. Coupled to the clarity of the Zu Gede cable, it explained my first impression of excess top energy where the same combination sounded perfectly balanced through the Rudistor NX33 or my McIntosh amplifier. All this is to say that component matching will be critical to get the most of what the HeadRoom Balanced Desktop has to offer. Start with a tonally dense and rich source and cables that offer a little bit of texture and harmonics of their own (think copper cables like Consonance's Billies or even the silver interconnects by Slinkylinks, which have an incredibly rich midrange beyond what one would normally expect from pure silver if one doesn't mind being robbed of ultimate level of bass extension).
Overall the Desktop is fairly accurate and detailed in the lower midrange of bass and baritone but things start sounding not quite as real as one ascends higher into the upper midrange. The first thing I noticed was brightness with violins which somewhat emphasized their metallic nature, leaving some of their wooden harmonics behind. When a Strad sounds all strings, you know something is amiss. But it was never as obvious as with Paul Agnew and William Christie's recording of Campra's Salve Regina [Virgin Classics 7243 5 45720 2 9]. I have been lucky enough to hear Paul Agnew in a couple of recitals over the past few years. Through the Desktop, he was lacking some of the intensity I remember from those concerts. The Rudistor NX-33 just sounded more natural in how it portrayed all the complex harmonics of Paul Agnew's voice and of Anne-Marie Lasla's viole de gambe. The Desktop did not sound bad or off, just not quite as rich and complex
as I would have liked, being rather lean, fast and precise, a presentation I am sure will seduce others.
With large orchestral works like Berlioz's Symphonie Fantastique directed by Riccardo Muti [Seraphim Classics 7243 5 73554-2-1], a flamboyant if not extremely lyrical interpretation by the Philadelphia Orchestra, the Balanced Desktop's dynamics were a fantastic asset especially in the fifth movement where a monstrous
Sabbath takes place after the hero's death and the Gothic "Dies Irae" theme gets perverted into a caricature of demons and witches (which got Berlioz in a fair amount of trouble with the Catholic church). Through the Desktop, violin pizzicatos were tight and clear, the bells loud and powerful and all three bell calls with their distinctive sounds intact, making it possible to hear deep into the orchestra even if the music did not unfurl fully into its usual 3-dimensional panorama, a headphone rather than Desktop issue. If anything, the ability to
listen deeply into the string section partially overcame the usual limitations of headphone listening.
On older recordings however like Richter's 1960 reading of Beethoven's First Piano Concerto with Charles Munch [RCA82876-59421-2], tape hiss was too bright to be ignored and eventually intruded in the listening experience. Through the competing Rudistor NX-33, recordings from the golden era of stereo took a whole new life for me which managed to put forward all their strengths and minimized tape noise by pushing it into the background. The Balanced Desktop just made it more difficult to ignore tape noise, one of the trade-offs that comes with analytical power.
The Desktop's external power supply allows for power cord swapping but I did not give it a try although to my great surprise, the amplifier proved extremely sensitive and responded very well to power conditioning. The Monster power unit I use did a great job of smoothing the top end not by removing detail but by adding fluidity and sweetness wherever it had been a bit short originally. If you invest in the Desktop Balanced, plug it into a power conditioner. I live in the countryside mostly surrounded by dairy farms. The difference was not insignificant so I can only imagine the benefit city dwellers will obtain from a similar piece of AC line equipment. But it was another, even cheaper piece of equipment that really drove home what the Desktop Balanced is capable of. You owe it to yourself to order the Desktop with its Home DAC module. With Headroom's 30-day return policy, the worst thing to happen is having to send it back and swapping it for a unit without the DAC if you don't like it. Unless your usual source costs far more than both CD players I had on hand (Musical
Fidelity A5 CD at $2500, the Atoll CD200 at $2000), I predict little risk of finding this investment wanting.
I have tried the Desktop DAC using my Accuphase DP55 as spinner via the Toslink connection as well as the Musical Fidelity A5 CD player. Both sounded equally detailed from the deepest bass to the upper treble and had slightly more texture than through the analog inputs (tremendously more actually when compared to the 10-year old DAC inside the DP55). Overall the sound was a little more refined and relaxed, like stepping up one level in a manufacturer's line, not a revolution but the elusive sense of added elegance and presence we all end up paying a lot of money for (often far more than this $399 upgrade). I know a $399 DAC lacks credibility but one reason for its giant performance may be that both the Desktop DAC and the Home upgrade (which I reviewed) are truly balanced designs. It is hard to imagine a simpler and more elegant way of getting a balanced signal directly from the digital feed to the amplification stages of the amp. The difference was easy to hear. Feeding the optical input of the DAC, I could not detect any harshness or excess brightness provided the amplifier was plugged into the power conditioner, otherwise the upper midrange remained a little stiff. What remained was the inherently lean character of the Desktop, aesthetically related to the Musical Fidelity Xcan but with more dynamics, bass, body, punch, detail and overall refinement. The DAC also includes a USB input which allowed further experiments even though harvesting all the potential of this connection was not as straightforward as I was hoping for partially because of owning a PC rather than Mac. That will teach me. If you have read here and there that Windows Media Player and all the basic music players developed for Windows XP and prior versions are worth little, I have to confirm that to be absolutely true. Connecting the Desktop and my laptop was a breeze. The laptop recognized the DAC and less than a minute later indicated that new hardware had been installed. That was about the only thing easy about the whole process.
Being an impatient individual, I threw a CD into the drive and listened. The sound lacked dynamics and detail. Dull is the best way to describe it. Think $200 DVD player, not really bad but nothing to write home about. On the other hand, watching Gerard Corbiau's Farinelli and being able to actually hear the computer-generated castrato voice with all its technical flaws was educational if not
musically satisfying. The castrato voice in this film was digitally mastered from recordings of the same arias by Derek Lee Ragin as counter tenor and Ewa Mallas-Godlewska as soprano. These transitions, harder to notice in a movie theatre, were more than obvious through earphones.
Then I remembered that most of the theoretical benefits should come from reading data from the hard drive. Sometimes theory works. I used Exact Audio Copy to write WAV files of a number of my favorite CDs to
magnetic drive and the improvements were significant - more detail, more depth but still fairly unexciting. The next step was to install Foobar2000 and again, detail retrieval went up a notch, dynamics increased, the top end gained in overall refinement and the treble lost most of its grain. I could feel I was on the right tracks but was running out of ideas on how to take it to the next level. I surfed the net and harvested bits and pieces of information to prepare for my next move. I have to admit that HeadRoom's complete absence of information on their website, on how to optimize the listening experience through the USB connection, was a little disappointing and certainly not on par with the quality of support otherwise available from their site.
One of Foobar's features is a PPHS resampler which I used to resample the 44.1kHz CD data to 96kHz before feeding it to the DAC. This little trick made the largest difference of all. I heard much deeper and more detailed bass, actually more detail throughout as though a veil had been removed which allowed the midrange and treble to sound their sweetest, better than my A5 CD player and its tubed output stage run
directly into the Desktop and on par with the Toslink digital input of the DAC. Only the Rudistor NX-33 was capable of a sweeter and overall more elegant reproduction of the highest register but there the NX-33 is in a class of its own. That the Desktop DAC/Foobar combination, set up properly, could even get close is amazing.
On Paganini's Violin Concerto No1 with Maxim Vengerov [Teldec 9031-73266-2], the HeadRoom amplifier and DAC managed to fully keep up with the tremendous speed of execution the Russian violinist is capable of and render more detail than I had ever heard from this disc while sounding less metallic than fed directly from the A5 CD player. Nevertheless, Vengerov's violin never sounded quite as sweet as it could have and did not display all the richness of tone I heard through the Rudistor NX-33 yet the latter could not deliver the sheer feeling of energy and rush this concerto should make you feel. Pick your poison then. This price level is still a land of compromises. When listening to Michael Haydn's Requiem [Hyperion CDA67510], I became fully aware of the technical qualities of the recording. I could hear deep into the musical mix and catch details I had not previously heard yet I experienced a more difficult time getting emotionally connected. The choir sounded a little more monochromatic than with the Rudistor, not made up of multiple tessitura but defaulting into a uniform voice of its own. The emotional expressiveness of the soloists did not come across quite as clearly either. It was a technically fine reproduction but did not trick me into feeling there.
After a few days of experimentation, I chose to permanently engage Foobar's equalizer. I did not hear any loss of detail from it and was able to use the 18-level equalizer to tailor a curve that better met my tastes. I designed it by ear and it exhibited a 2 to 3dB trough from 622Hz to 3.5kHz! The original curve I had designed also had a treble roll-off above 7kHz but after I plugged the amplifier into my power conditioner, this correction did not prove necessary. The treble could be left alone for life and sparkle without aggression, just not quite the level of sweetness and elegance the NX-33 delivered.
While surfing left and right on the net, I found many articles indicating that ASIO drivers are the way to get ultimate quality from USB DACs, marrying high speed, low latency and direct communication between DAC and computer and bypassing all of Windows' nefarious programs. From ASIO-compatible sound cards to true ASIO software/hardware solutions, there are a few options to get the ultimate sound quality from a computer.
Not being that dedicated, I tried the ASIO4all route. ASIO4all is freeware which emulates ASIO through some Windows components. It is not a true ASIO driver but usually considered a good substitute. Unfortunately I found the program temperamental and had to uninstall/reinstall it multiple times to achieve a fully functional setup. It's not that the program had any issue recognizing the DAC to allow me to set it up. Nor had the DAC any issue with Foobar either even though that setup procedure was not entirely straightforward. The issue had more to do with my inexperience. As I was trying various solutions to see what would sound best, I apparently picked configurations that ASIO4all did not like (like engaging the 96kHz resampler and a number of cross-feed softwares I wanted to compare to HeadRoom's hardware solution and never got a chance to make work). Once I picked one of those incompatible settings, there was no way to come back. ASIO4all refused any and all sound through the DAC and even rebooting the computer did nothing. I had to uninstall and overwrite the software and go through the whole setup procedure again (which I did over five times). In the end, I listened to Foobar and ASIO4all with no upsampling and no equalization. This seemed to create the fewest glitches. If there was any advantage to this over the non-ASIO setup with upsampling and equalization, I could not hear it. Actually, I preferred the non-ASIO sound in most cases because the benefits of 96kHz upsampling and equalization far outweighed all supposed benefits from ASIO4all. The last blow against ASIO4all which triggered its permanent removal from my computer was its inability to play any non 44.1kHz signal. This bugged me after I had downloaded hi-resolution 96kHz FLAC transfers of master tapes from High Definition Tape Transfers. When I crashed the ASIO driver once more, I remembered a few choice French curses, un-installed the program and considered myself cured. Those master files have so much detail, life and ambiance that I really did not feel it worthwhile to downsample to 44.1kHz and lose most of the benefits of high resolution. If you run a computer-based system, you probably should take the time to download this company's four hiresolution tape transfer samples and give them a listen. I particularly loved the presence of the organ in Saint-Saens' 3rd Symphony. I never before had heard the air rushing out of the pipes in this fashion.
All along this review, I felt conflicted about the Desktop Balanced. I couldn't help but admire its sense of timing and rhythm, its deep, powerful and detailed bass, the incredible flexibility and range of options, which the Home DAC brings to the table. Conversely, I never managed to completely engage and dive into the music as I can with my reference gear. I I have tried to pinpoint the root cause for that and I am not sure I succeeded. The Desktop, unlike the NX-33, is a great reviewer's tool, passing even the slightest nuances between cables for example. The Desktop would be the better of the two amps at recording monitoring. Its slightly forward upper midrange would draw immediate attention to any issue. Ultimately however, I missed the organic and fluid Rudistor, its ultimate level of refinement, its ability to make me forget my reviewer's hat and focus on the music instead. On the other hand, if you expect your headphone system to be a magnifying glass that lets you hear into a recording in ways that are far more detailed than any speaker system will ever provide; and if you are willing to leave tonal accuracy, harmonics and flow a little behind to do so - then the Balanced Desktop should be right on top of your shopping list. If your headphones of choice are HD650s, then the Balanced Desktop is your winning ticket to take those cans to a completely different level of performance. It will give them the life and energy they otherwise can be short of.
The Balanced Desktop and Rudistor Nx-33 give two fundamentally different readings of the same music. My personal preference goes to the organic sounding Nx-33 but it is nothing more than that, a preference. I don't believe one is necessarily better than the other but I do know that they will not please the same audiophiles. Ultimately, it is better that way. It would be very
boring indeed if we all liked the same things.
